Known in the state of the art are ophthalmologic devices and ophthalmologic measuring methods in which, by means of a light projector, a beam of rays is projected through a cross-sectional portion of an eye, in particular through a cross-sectional portion of the cornea. Typically, the beam of rays is projected in the form of a light slit. Described in the patent publication U.S. Pat. No. 5,404,884 is a method and a device for examining corneal tissue of a patient. According to U.S. Pat. No. 5,404,884, a substantially planer laser beam with a slit-like profile is directed through a cross-sectional portion of the cornea. By capturing at least a portion of the light scattered in the cornea, i.e. at least a portion of the light slit, a cross-sectional image of the cornea is obtained, according to U.S. Pat. No. 5,404,884. From a multiplicity of such cross-sectional images of the cornea, corneal haze, corneal thickness and corneal topography can be determined comprehensively for the whole cornea, according to U.S. Pat. No. 5,404,884. Since the eyes can move relative to the examination device, examination of the entire eye as set forth in U.S. Pat. No. 5,404,884 can lead to inaccuracies, however, because these relative movements are not registered and taken into account. In the professional article B. R. Masters et al., “Transformation of a Set of Slices Rotated on a Common Axis to a Set of Z-Slices: Application to Three-Dimensional Visualization of the In Vivo Human Lens,” Computerized Medical Imaging and Graphics, Vol. 21, No. 3, pages 145 to 151, 1997, it is explicitly pointed out moreover that with comprehensive examination of the eye based on the merging of a multiplicity of cross-sectional images, measurement artifacts can result as a consequence of the difficulty of mutual alignment of the individual cross-sectional images.
Described in the patent publication U.S. Pat. No. 4,711,541 is an ophthalmologic device having a slit lamp for projection of a light slit on the lens of an eye. The device according to U.S. Pat. No. 4,711,541 comprises in addition a photo camera disposed according to Scheimpflug conditions with respect to the plane of the light slit in order to image sharply the entire cross-sectional portion of the crystalline lens which is illuminated by the light slit. The device according to U.S. Pat. No. 4,711,541 has a stereo microscope in order to enable the user to have a top view of the eye. By means of optical elements of the device, the top view can be supplied to the camera for depiction. However, by means of polarizing filters, it is thereby ensured that not the light slit reflected on the surface of the crystalline lens but instead only the background illumination of the eye, visible in the top view, coming from the reflection of the light slit on the ocular fundus and the scattering by the crystalline lens, is supplied to the photo camera for imaging. By means of a movable mirror, the light section in the crystalline lens and the top view of the eye with the background illumination can be pictured next to each other on the same photograph. Since the device according to U.S. Pat. No. 4,711,541 only allows an examination with individual pictures, no coherent examination of the whole eye can be carried out.
Described in the patent publication U.S. Pat. No. 5,341,180 is an ophthalmologic photographing apparatus which projects a light slit on the eye by means of a slit lamp. The photographing apparatus comprises a CCD camera (Charged Couple Device) which is disposed with respect to the plane of the light slit according to Scheimpflug conditions, in order to image sharply the entire cross-sectional portion of the eye illuminated by the light slit. The apparatus according to U.S. Pat. No. 5,341,180 comprises a second CCD camera providing the user with a top view of the eye to be examined and serving to align the apparatus, or respectively the eye, with the aid of light markers projected on the eye. The apparatus according to U.S. Pat. No. 5,341,180 has polarizing filters in order to prevent the light slit from being visible in the top view of the second CCD camera. In order to facilitate precise alignments, the patient to be examined has to focus his eyes on fixing markers with the taking of each picture, which the patient can find tedious during an examination of the entire eye and which is also time-consuming.